The present invention relates to an infrared-transmissive lens made of chalcogenide glass and a human body detecting sensor including the lens and a pyroelectric infrared sensor.
Human body detecting sensors using pyroelectric infrared sensors are widely used in the field of home electric appliances and industrial equipments. The sensors are used, for example, to open and close a door, to operate a water tap for a toilet bowl and to operate an air conditioner. Generally, a filter for transmitting only infrared rays is provided before an infrared sensor in order to collect infrared rays having a wavelength of 8 to 12 .mu.m emitted from a human body effectively. These filters have heretofore been made of silicon, germanium and metal halide.
FIG. 2 schematically illustrates an example of a conventional human body detecting sensor. As shown in FIG. 2, a lens 12 is disposed before a plurality of pyroelectric infrared sensors 11 (only one sensor is shown in the drawing for clarification) arranged side by side and the lens 12 is moved right and left to send an image to the pyroelectric infrared sensor. A lens driver for moving the lens is disposed in alignment with the lens in the vertical direction and hence the driver is not shown. Electrodes 13 for obtaining a voltage generated by the pyroelectric infrared sensor 11 are disposed on both sides of the infrared sensor 11 and a chopper 14 for intensity-modulating the infrared rays is disposed before the infrared sensor 11. The chopper is rotated at a constant speed by a chopper driver 15. Further, the infrared sensor 11 is supported by supporting rods 16 and an output signal of the infrared sensor 11 is delivered by lead wires 17 to outside.